“When bodhisattvas joyously persevere, prior to actively engaging themselves they put on the armor of a preliminary enthusiastic thought such as, ‘For a trillion sets of three immeasurably great eons each composed of days as long as a thousand great eons, I shall not relinquish my practice of joyous perseverance. For the sake of relieving the suffering of a single living being, I would rejoice at remaining only as a hell-being until I attain buddhahood. As I exert myself in this manner for the sake of complete enlightenment, what need is there to mention my perseverance over a shorter period or in the face of lesser suffering?’ Such is the joyous perseverance that is like armor. A bodhisattva who produces even an aspiration for, or just faith in, such joyous perseverance is steadfast.”
From The Great Treatise on the Stages of the Path to Enlightenment: The Lam Rim Chen Mo by Tsong Khapa. Translated by the Lamrim Chenmo Translation Committee. Snow Lion/Shambhala Publications.